1. Field of the Invention
The present invention relates to a sensor probe for use in board inspection, more particularly to a sensor probe for inspecting a circuit board having a microscopic wiring pattern, and a manufacturing method thereof.
2. Prior Art
For inspecting a circuit board having a microscopic pattern, an inspection signal has hitherto been applied to a number of pins which had been pressed to respective terminals of a board as an object to be inspected. In this method, a rubber sheet is provided on the board in order to reduce the load which is caused from the press of the number of pins and applied to the board. This often causes a problem of loose connection due to the rubber sheet interposed between the pins and the board.
To solve this problem, for example, in Japanese Patent Laid-Open Publication No. Hei 9-264919, applied for by the present, applicants, there is provided a method for inspecting a defect of a board in such a way that a signal is picked up on a non-contact basis by use of a probe (electrode) having a size lager than a width of a wiring pattern as an inspecting object.
Japanese Patent Laid-Open Publication No. Hei 8-278342 also discloses electrodes (stimulator) 11A and 11B for generating an inspection signal toward a board and a plurality of electrodes 12A, 12B, 12C, . . . for receiving a radiation signal from the board, as shown in FIG. 1.
The common idea among Japanese Patent Laid-Open Publications Nos. Hei 9-264919 and Hei 8-278342 is to inspect a plurality of pattern lines by an electrode having a size as large as that capable of covering the pattern lines in a lump and also on a non-contact basis.
Sensor probes which are used in Japanese Patent Laid-Open Publications Nos. Hei 9-264919 and Hei 8-278342 are intended to inspect a circuit pattern having a pitch and size as large as those of a typical printed circuit board, and their integration degree is in low level. Therefore, subject to forming their sensor electrode portion by means of a particular process, such as machining and simplified etching, sufficient accuracy would be obtained.
In those sensor probes of the prior art, the electrode having the size as large as that capable of covering a plurality of pattern lines is used to eliminate the need for high alignment accuracy. Thus, these sensor probes can neither inspect a particular size of circuit pattern, for example approximately 50 μm or not greater than 50 μm, with high resolution, nor apply to a circuit board in which the wiring pattern branches along its way. In addition, it is impossible to inspect a defective status in which the pattern is not completely broken and is partly chipped away.